[en] High-performance flexible strain sensors based on maleic anhydride-grafted styrene-butadiene-styrene triblock copolymer/carbon black (SBS-g-MAH/CB) composites were prepared by simple solvent swelling of SBS-g-MAH/CB composites obtained by melt blending. After swelling in N,N-dimethylformamide (DMF) or xylene, the aggregation of CB in the composites was reduced noticeably. Consequently, the conductivity of the composites improved by a great extent, and the percolation thresholds of the composites decreased. At 12% CB loading, the conductivity increased approximately 400 times or 6000 times upon swelling in DMF or xylene, respectively. DMF swelling did not change the morphology of SBS-g-MAH, and a three-dimensional conductive network was formed in the composites. The SBS-g-MAH morphology changed considerably, and a two-dimensional conductive network was formed after swelling in xylene. DMF swelling enhanced the piezoresistive performance of the composites. The gauge factor increased from 4 to 71. Moreover, the drawbacks of composites prepared by melt blending, including electromechanical inconsistency and poor stability, were overcome. Due to the high conductivity and the change in SBS-g-MAH morphology, an approximately two-fold increase in electromagnetic interference shielding efficiency was observed after swelling the composites in xylene. The mechanism of the strain sensor was discussed. The strain sensing behaviour of SBS-g-MAH/CB composites can be explained by an analytical model based on the tunneling theory. (paper)

[en] The bubble G15.684-0.29 has a radius of 15.7 pc. Its large size indicates that it may have enough time to trigger star formation. We identify 39 dense cold clumps around the bubble from the Hi-GAL survey. All of them satisfy the criteria for forming massive stars, and most of them lie in the bubble shell. We identify 19 molecular clumps around the bubble from the ¹²CO(3–2) survey, all of which are gravitationally bound. We found 9 Class I YSOs, 28 Class II YSOs, and 12 transition disks (TDs) around the bubble. For those young stellar objects (YSOs) located within the bubble boundary, 6 of 7 Class I YSOs lie in the shell, 15 of 22 Class II YSOs lie inside the bubble, and 3 of 5 TDs lie inside the bubble. The dynamical age of G15.684-0.29 in a turbulent medium is ∼4 Myr, which is much greater than the shell fragmentation time, ∼0.82–1.74 Myr. We suggest that triggered star formation may be ongoing in the shell of the bubble, and the collect and collapse model may work here. However, we cannot rule out the possibility that the radiation-driven implosion model may work on the formation of some YSOs. As we expected, the larger bubble has a much longer dynamical age, but we failed to find a clear age gradient for YSOs around the bubble.

[en] We mapped the kinetic temperature structure of Orion KL in a ∼20″ (∼8000 au) sized region with para-H₂CS 7₀₇ − 6₀₆, 7₂₆ − 6₂₅, and 7₂₅ − 6₂₄ making use of Atacama Large Millimeter/submillimeter Array Band 6 Science Verification data. The kinetic temperatures obtained with a resolution of 1.″65 × 1.″14 (∼550 au) are deduced by modeling the measured averaged velocity-integrated intensity ratios of para-H₂CS 7₂₆ − 6₂₅/7₀₇ − 6₀₆ and 7₂₅ − 6₂₄/7₀₇ − 6₀₆ with a RADEX non-LTE model. The kinetic temperatures of the dense gas, derived from the para-H₂CS line ratios at a spatial density of 10⁷ cm⁻³, are high, ranging from 43 to >500 K with an unweighted average of ∼170 K. There is no evidence for internal sources playing an important role in the heating of the various structures identified in previous work, namely the elongated ridge, the northwestern clump, and the eastern region of the compact ridge, while the high temperatures in the western region of the compact ridge may be dominated by internal massive star formation. Significant gradients of kinetic temperature along molecular filaments traced by H₂CS indicate that the dense gas is heated by the shocks induced by the enigmatic explosive event which occurred several hundred years ago and greatly affected the energetics of the Orion KL region. Thus, with the notable exception of the western region of the compact ridge, the high temperatures of the dense gas in Orion KL are probably caused by shocks from the explosive event, leading to a dominant component of externally heated dense gas.

[en] Highlights: • A consistent description of critical temperature degradation of single- and polycrystal Nb3Sn under hydrostatic pressure is developed. • The model simulations qualitatively agree with the experimental observations. • Role of grain boundary deformation in the critical temperature degradation of Nb3Sn under high pressure is revealed. -- Abstract: Variation of the critical superconducting properties of Nb₃Sn material in terms of mechanical deformation has not been well determined. Fundamental understanding of electromechanical coupling effects is significant in the analysis and construction of high magnetic field superconducting magnet. Considering the microstructure deformation and its inner relationship with normal state resistivity evolution, we developed a consistent description of critical temperature degradation responses of single- and polycrystal Nb₃Sn under hydrostatic pressure. The model simulations qualitatively agree with the experimental observations. Based on the polycrystalline finite element method, the analysis carefully examines the role of grain boundary deformation in the critical temperature degradation of superconducting Nb₃Sn under high pressure. The grain boundary deformation-related effect is responsible for the obvious degradation differences between polycrystal and single crystal Nb₃Sn under the same level of pressure. The results are helpful for understanding the empirical relation presented by the experiment and opens the way for the parameterization of the strain sensitivity of the superconducting Nb₃Sn material.

[en] Highlights: • Occurrence of alkenones from Lake Tuosu over the last ∼1200 years. • Abnormal warm and saline alkenone signals in the centennial cool-wet periods. • Opposite relation between alkenone records and virtue climates in Lake Tuosu. • Specie turn-over might be the reason for the abnormal warm-saline alkenone signals. Paleoclimatic reconstructions on the arid/semi-arid northern Tibetan Plateau are important for understanding the complex interactions between the mid-latitude westerly and subtropical Asian monsoon circulations. The development of paleoclimatic reconstructions largely relies on the invention and application of proper quantitative/semi-quantitative temperature and salinity proxies. Over the last few decades, alkenones have shown great potential as indicators of the past temperatures and salinities of lakes on the northern Tibetan Plateau. Several alkenone-based temperature and salinity records have confirmed centennial warm-dry and cold-wet variations during the Holocene on the northern Tibetan Plateau. Herein, we present alkenone-based records from Lake Tuosu in the Qaidam Basin over the last ∼1200 years. The alkenone signals show similar characteristics to published alkenone records in the nearby region during centennial warm periods (the Medieval Warm Period and Current Warm Period). However, the alkenones from Lake Tuosu demonstrate abnormally warm and saline signals during centennial cold periods (mainly during the Little Ice Age), in contrast to the widely recognized cold-wet conditions in the Qaidam Basin. Accordingly, the alkenone records from Lake Tuosu provide an exceptional case for the application of alkenones. The abnormally warm and saline alkenone signals from Lake Tuosu during centennial cold periods cannot be explained by either the presence of the C_37:3 alkenone isomer or seasonal bias in alkenone production. Changes in species composition might be an alternative reason for this, which requires a further investigation of the sources of alkenones in lakes in the future.

[en] Combining infrared and submillimeter observations and applying a two-temperature modified blackbody (TMBB) model with a hierarchical Bayesian technique, we model the spectral energy distribution of 12 nearby dwarf irregular (dIrr) galaxies. We aim to probe potential submillimeter excess emission at 350, 500, and 850 μm and investigate the properties of cold dust parameters. Based on the TMBB model with cold dust emissivity index (β_c) fixed to 2, one galaxy shows 500 μm excess emission and nine galaxies show excess at 850 μm (five of them still show 850 μm excess in the case of free β_c). We find that the 850 μm excess emission is easily detected in the dIrr galaxies with low star formation activity. The 850 μm excess is more frequent and more prominent in dIrr galaxies with low molecular hydrogen gas mass fraction or low ratios between cold dust mass and gas mass. As galaxies evolve, the ratios between atomic hydrogen gas mass and stellar mass decrease and the 850 μm excess emission tends to decrease or even disappear. Our results suggest that the cold dust temperature may increase, as the dIrr galaxies have more intense star formation or richer metallicity. There is a weak anticorrelation between the cold dust-to-stellar mass ratio and the specific star formation rate for our galaxies.